1. Field of the Invention
The invention relates to an apparatus for conveying viscous material.
2. Description of the Related Art
Such an apparatus is known, for example, from DE 10 2004 030 654 A1. It serves for conveying viscous material, such as, for example, adhesives, sealants or insulation materials, out of a barrel-like container, for example toward an application apparatus. In this connection, the container is closed off, toward the top, by a follower plate that follows the course of the material level in the container, which decreases during the course of the conveying process and, in this connection, lies against the inner surface of the container wall, forming a seal. The follower plate has a dome in the center, which extends upward from an underside of the follower plate. The follower plate applies slight pressure to the material, lying against it, and opens into a material exit opening. A pump conveys the viscous material through the material exit opening with operating pressure.
Once emptied, a container is replaced with a full container. In this connection, either the follower plate remains at the bottom in the emptied container, and the pump is uncoupled from it, so that the container along with the follower plate can be transported to a filling station, in which new material is filled in through the material exit opening, until the follower plate forms the upper end of the container once again, or the follower plate connected with the pump is pulled out of the container, and the container is transported away to be filled again. A filled container is placed under the pump and, in the case of the first alternative described above, the pump is set onto the dome, while in the case of the second alternative described above, the follower plate connected with the pump is set onto the material contained in the container. In both cases, however, the problem exists that air can collect in the dome and/or in an end region of the pump, with which air the material conveyed after refilling is mixed. In order to achieve reliable material application, the air or material contaminated with air must therefore first be pumped away; this material cannot be used and must therefore be disposed of. This venting takes place manually, in that a worker pumps material out of the container until this material no longer contains any air. This method is imprecise. In order to ensure that the material that has been pumped away is usable, the tendency therefore is to pump away too much material, in case of doubt. Pumping away too much material is particularly disadvantageous if this material is expensive, and this material generally has to be disposed of as hazardous waste.